Image processing apparatus and method

ABSTRACT

An image processing apparatus is constructed by an input unit to input image data, a setting unit to set a color space compression processing mode on the basis of a kind of signal format of the inputted image data, and a color space compression processing unit to execute a color space compressing process to the inputted image data on the basis of the set color space compression processing mode. The color space compression processing mode has a first mode in which the color space compression is executed and a second mode in which the color space compression is not executed. In case of the CMYK signal format, the second mode is set. In case of the RGB signal format, the first mode is set.

This is a continuation of Ser. No. 08/413,431 filed Mar. 30, 1995 nowabandoned.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates to an image processing apparatus and method forperforming a color space compression.

2. Related Background Art

In recent years, there has been considered a color space compressingtechnique for converting an input color signal to an optimum colorsignal within a color reconstructing range in which an originalexpressed by the input color signal including a signal out of a colorreconstructing range of an output device can be reconstructed by theoutput device.

According to the conventional color space compressing technique,however, a color space compression based on an input image cannot beperformed.

There is, consequently, a problem such that, for example, in spite ofthe fact that a color space compressing process has been performed by ahost apparatus, the color space compressing process is again executed byan image processing apparatus and it takes a long processing time thanit is needed or a reproduction image deteriorates.

SUMMARY OF THE INVENTION

It is an object of the invention to provide image processing apparatusand method which can select whether a color space compression isexecuted or not on the basis of input image data.

Another object of the invention is that a color space compression isperformed to an image signal obtained by scanning an original and acolor space compression is not executed to an image signal from anexternal apparatus, thereby preventing that a color space compressingprocess is executed to the same image a plurality of number of times.

To accomplish the above objects, according to a preferred embodiment ofthe invention, there is provided an image processing apparatuscomprising: input means for inputting image data; setting means forsetting a color space compression processing mode on the basis of a kindof signal format of the inputted image data; and color space compressionprocessing means for performing a color space compressing process to theinputted image data on the basis of the set color space compressionprocessing mode, wherein the color space compression processing mode hasa first mode in which a color space compression is performed and asecond mode in which the color space compression is not performed.

The above and other objects and features of the present invention willbecome apparent from the following detailed description and the appendedclaims with reference to the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1, comprised of FIGS. 1A to 1D, is a block diagram showing anembodiment of an image processing apparatus of the present invention;

FIG. 2 is a constructional diagram showing an embodiment of the imageprocessing apparatus using the invention;

FIG. 3 is a block diagram showing an embodiment of a color spacecompression circuit in the image processing apparatus of the invention;

FIG. 4 is a flowchart showing an example of image processes of theinvention;

FIG. 5, comprised of FIGS. 5A to 5D, is a diagram showing an example ofa console unit for the user to instruct the image processing apparatusof the invention;

FIG. 6 is a diagram showing another example of the console unit for theuser to instruct the image processing apparatus of the invention;

FIG. 7, comprised of FIGS. 7A and 7B, is a diagram showing anotherexample of the console unit for the user to instruct the imageprocessing apparatus of the invention;

FIG. 8 is a diagram showing another example of the console unit for theuser to instruct the image processing apparatus of the invention;

FIG. 9 is a diagram showing a combination of modes shown in theembodiment 2 of the invention;

FIG. 10 is a diagram showing an example of a light amount-densityconversion that is executed in an LOG conversion unit in the imageprocessing apparatus of the invention;

FIG. 11 is a block diagram showing another embodiment of the color spacecompression circuit described in the embodiment 1 of the invention; and

FIG. 12 is a diagram showing an example of a flow of signals between anexternal apparatus and the image processing apparatus.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

<Embodiment 1>

The first embodiment of the invention will now be described in detailhereinbelow with reference to the drawings.

(Construction of main body)

FIG. 2 is a schematic cross sectional diagram showing an example of acolor image processing apparatus of the embodiment.

The embodiment has a digital color image reader unit in an upper portionand a digital color image printer unit in a lower portion.

In the reader unit, an original 30 is placed on an original supportplate glass 31. A well-known original scanning unit including anexposure lamp 32 is exposed and scanned by an optical system read drivemotor 35 at a predetermined speed according to a preset copymagnification. A reflected light image from the original 30 is convergedonto a full-color sensor (CCD) 34 through a lens 33, thereby obtaining acolor separation image signal. As a full-color sensor, CCDs of threelines attached with filters of R (red), G (green), and B (blue) arrangedso as to be neighboring each other are used. Color separation imagesignals are subjected to image processes by an image processing unit 36and a controller unit 37 and the processed signals are supplied to theprinter unit.

A console unit 51 (which will be explained hereinlater) is providedaround the original support plate glass 31. Switches to set variousmodes regarding a copy sequence, a display screen to display, and adisplay apparatus are arranged.

In the printer unit, a photosensitive drum 1 as an image holding memberis held so as to be rotatable in the direction of an arrow. Apre-exposure lamp 11, a corona charging device 2, a laser exposureoptical system 3, a potential sensor 12, four developing devices 4 y, 4c, 4 m, and 4Bk of different colors, means 13 for detecting a lightamount on the drum; a transfer apparatus (5 b to 5 h), and a cleaningdevice 6 are arranged around the photosensitive drum 1.

In the laser exposure optical system 3, an image signal from the readerunit is converted to a light signal by a laser output unit (not shown).The converted laser beam is reflected by a polygon mirror 3 a and passesthrough a lens 3 b and a mirror 3 c and is projected to the surface ofthe photosensitive drum 1.

When the image is formed in the printer unit, the photosensitive drum 1is rotated in the direction of an arrow. After the photosensitive drum 1was discharged by the pre-exposure lamp 11, the drum 1 is uniformlycharged by the corona charging device 2. A light image E is irradiatedevery separation color and a latent image is formed.

Subsequently, a predetermined developing device is made operative andthe latent image on the photosensitive drum 1 is developed, therebyforming a toner image made of a resin as a base substance onto thephotosensitive drum 1. The developing device is alternatively allowed toapproach the photosensitive drum 1 in accordance with each separationcolor by the operations of eccentricity cams 24 y, 24 m, 24 c, and 24Bk.

Further, the toner image on the photosensitive drum 1 is transferred toa recording member supplied from one of recording member cassettes 7 a,7 b, and 7 c which has previously been selected to a position whichfaces the photosensitive drum 1 through a conveying system and atransfer apparatus 5. The selection of the recording member cassette isperformed by previously driving either one of pickup rollers 27 a, 27 b,and 27 c by a control signal from the controller unit 37 in accordancewith a size of recording image.

In the embodiment, the transfer apparatus 5 has: a transfer drum 5 a; atransfer charging device 5 b; an adsorption roller 5 g which faces anadsorption charging device 5 c for electrostatically adsorbing therecording member; an inside charging device 5 d; and an outside chargingdevice 5 e. A recording member holding sheet 5 f made of a dielectricmaterial is cylindrically integrally suspended in a peripheral surfaceopen area of the transfer drum 5 a that is axially supported so as to berotated. A dielectric material sheet such as a polycarbonate film or thelike is used as a recording member holding sheet 5 f.

As the drum-shaped transfer apparatus, namely, the transfer drum 5 a isrotated, the toner image on the photosensitive drum is transferred ontothe recording member held on the recording member holding sheet 5 f bythe transfer charging device 5 b.

A desired number of color images are transferred to the recording memberthat is adsorbed to the recording member holding sheet 5 f and isconveyed, thereby forming a full-color image.

In case of forming a full-color image, after completion of the transferof the toner images of four colors as mentioned above, the recordingmember is separated from the transfer drum 5 a by functions of aseparating nail 8 a, a separation pushing-up roller 8 b, and aseparation charging device 5 h and is ejected onto a tray 10 through athermal roller fixing device 9.

On the other hand, after completion of the transfer of the toner images,the residual toner on the surface of the photosensitive drum 1 iscleaned by the cleaning device 6. Subsequently, the drum 1 is againsubjected to the image forming processes.

In case of forming images on both sides of the recording member, aconveying path switching guide 19 is soon driven after the recordingmember was ejected out of the fixing device 9. The recording memberpasses through a conveying vertical path 20 and is once guided to areversing path 21 a. Afte r that, a rear edge of the recording memberwhen it is fed is set to a front edge by the reverse rotation of areversing roller 21 b and the recording member is moved backward in thedirection opposite to the feeding direction and is enclosed into anintermediate tray 22. Subsequently, an image is again formed ontoanother side by the foregoing image forming processes.

To prevent a dispersion and deposition of powder onto the recordingmember holding sheet 5 f of the transfer drum 5 a, a deposition of anoil onto the recording member, or the like, a cleaning operation isperformed by functions of a far brush 14 and a backup brush 15 whichfaces the brush 14 through the recording member holding sheet 5 f and byfunctions of an oil removing roller 16 and a backup brush 17 which facesthe roller 16 through the recording member holding sheet 5 f. Such acleaning operation is performed before or after the image formation.When a jam (paper jam) occurs, such a cleaning operation is executed anytime.

In the embodiment, an eccentricity cam 25 is made operative at a desiredtiming and a cam follower 5 i which is integrated with the transfer drum5 a is made operative, thereby enabling a gap between the recordingmember holding sheet 5 f and the photosensitive drum 1 to be arbitrarilyset. For example, in a standby state or when the power source is turnedoff, the transfer drum and the photosensitive drum is away from eachother.

(Image processing block)

FIGS. 1A to 1D show an image processing unit, a controller unit, andtheir peripheral units to be controlled. The full-color sensor (CCD) 34is constructed by CCDs 101, 102, and 103 of three lines of red, green,and blue and color separates light information of one line from theoriginal and outputs electric signals of R, G, and B at a resolution of400 dpi. In the embodiment, since an image of maximum 297 mm(longitudinal direction of the A4 size) is read as one line, an image of4677 pixels of one line for each of R, G, and B is generated from theCCD. Reference numeral 104 denotes a sync signal generation circuitconstructed by a main scan address counter, a sub scan address counter,and the like. The main scan address counter is cleared by a BD signal asa sync signal for laser recording of each line to the photosensitivedrum, counts a VCLK signal from a pixel clock generator 105, andgenerates a count output H-ADR corresponding to each pixel of the imageinformation of one line read out from the CCD 34. As for the countoutput H-ADR, the counter counts up from 0 to 5000 and the image signalof one line from the CCD 34 can be sufficiently read out. The syncsignal generation circuit 104 generates various kinds of timing signalssuch as line sync signal LSYNC, main scan effective interval signal VEand sub scan effective interval signal PE of the image signal, and thelike.

Reference numeral 106 denotes a CCD drive signal generation unit fordecoding the count output H-ADR and generates a set pulse and aCCD-DRIVE signal as a transfer clock from a shift pulse of the CCD.Thus, the color separation image signals of R, G, and B for the samepixel are sequentially outputted from the CCD synchronously with asignal VCLK. Reference numeral 107 denotes an A/D converter forconverting each of the image signals of red, green, and blue into thedigital signal of eight bits.

Reference numeral 150 denotes a shading correction circuit forcorrecting a variation of a signal output of every pixel in the CCD. Theshading correction circuit has a memory of one line of each of thesignals of R, G, and B and reads an image of a white board having apredetermined density by the optical system and uses the read imagesignal as a reference signal.

Reference numeral 151 denotes a sub-scan threading circuit for absorbingthat the image signal read by the CCD is deviated in the sub scandirection by eight lines at a time.

Reference numeral 152 denotes an input masking circuit for eliminating acolor turbidity of each of the input signals R, G, and B by a matrixarithmetic operation of (3×3).

Reference numerals 153, 163, and 167 denote buffers each for allowingthe image signal to pass when a ZO-ED signal is at the L level and forpreventing that the image signal passes when the ZO-ED signal is at theH level. Ordinarily, the ZO-ED signal is at the L level when using anediting function.

In an editing circuit unit 154, reference numeral 155 denotes a filterfor smoothing the image signal and a matrix arithmetic operation of(5×5) is performed.

Reference numeral 156 denotes a color conversion circuit havingfunctions for converting the image signals of RGB to color spacecoordinates of HSL, converting the color which has previously beendesignated in an HSL color space to another designated color, and againreturning to the color space of RGB.

Reference numeral 159 denotes an external apparatus such as IPUconstructed by a memory apparatus for storing the image signal of up tothe A3 size, a computer for controlling the memory apparatus, and thelike, host computer for performing various image processes, filmscanner, or the like.

The external apparatus inputs and outputs the image signals in a form ofparallel signals of red, green, and blue (RGB), area-sequential imagesignals of cyan, magenta, yellow, and black (CMYK), binary signal, orthe like.

In case of inputting the CMYK area-sequential image signals, the imagesignals are transferred by using an R line.

Between the external apparatus 159 and the image processing apparatus,in addition to the image signals as mentioned above, the communicationof an IPU-BI signal and a status command is executed by using onechannel which can perform a two-way communication.

The IPU-BI signal is a 1-bit signal and can be used as, for example, aparameter control for various image processes, an area signal, or thelike.

The status command is used in the sync signal or a protocol that isexecuted at the time of turn-on of the power source or at the time ofimage communication.

FIG. 12 shows a communication between the external apparatus and theimage processing apparatus.

In the protocol at the time of turn-on of the power source, an externalapparatus name 123 and a function 125 are sent from the externalapparatus 159 to the image processing apparatus. Similarly, an imageprocessing apparatus name 124 and a function 126 are sent from the imageprocessing apparatus to the external apparatus.

In the protocol at the time of image communication, a processing order127 and a mode set 128 of the IPU-BI signal are sent from the externalapparatus 159 to the image processing apparatus. The sync signal is sentfrom the image processing apparatus to an engine in order to synchronizea transfer image signal.

Reference numeral 158 denotes an interface (I/F) circuit for matchingthe timings and speeds between the image signal from the externalapparatus and the internal image signal.

Reference numeral 160 denotes an area generation circuit for generatingand storing information indicative of an area designated by an editor orthe like. A MARKER signal in which an image signal of a marker pen orthe like drawn on the original was extracted can be also used as anarea. An SC-BI signal in which the image signal read by the CCD wasbinarized is used as an independent area signal for a Z-BI outputsignal.

Reference numeral 157 denotes a synthesizing (1) circuit forsynthesizing the RGB signal read by the CCD and the RGB image signal orYMCK image signal from the external apparatus 159. An area to besynthesized is designated by an AREA signal from the area generationcircuit 160 or the IPU-BI signal from the external apparatus. Areplacement synthesis and an openwork synthesis are executed in thesynthesizing (1) circuit 157. The replacement synthesis in which theimage signal from the CCD and the image signal from the externalapparatus are independently synthesized every area (either one of theimage signals is selected every pixel), the image signal from the CCDcan be synthesized to the RGB or CMYK image signal from the externalapparatus. On the other hand, in the openwork synthesis in which twoimages are simultaneously synthesized so as to be overlapped andopenworked (both of the image signals are mutually operated everypixel), the image signal from the CCD can be synthesized to only the RGBsignal from the external apparatus of the same signal format. Further, asynthesis of the RGB image signal from the CCD and the binary image fromthe external apparatus or the like can be also performed. In theopenwork synthesis, an openwork ratio indicating which amount of whichone of the two images is synthesized so as to be openworked can be alsodesignated.

The designation of the area in the replacement synthesis is performed onthe basis of the IPU-BI signal or the area signal formed by the areageneration circuit 160.

That is, in case of designating the area on the external apparatus side,the IPU-BI signal is used. In case of designating the area on the imageprocessing apparatus side such as a digitizer or the like, the areasignal is used. A CPU 130 controls the synthesizing (1) circuit on thebasis of the area designation.

In case of using the IPU-BI signal, a mode such that the CPU 130analyzes the IPU-BI signal mode set 128 as a status command in theprotocol and the IPU-BI signal is used for area designation of thereplacement synthesis is set.

After that, the IPU-BI signal passes through a signal line by which anarea signal which is produced by the area generation circuit 160.

Reference numeral 161 denotes a contour generation circuit forextracting a contour for the SC-BI signal in which the image signal readby the CCD was binarized, the IPU-BI signal as binary data from theexternal apparatus, or the Z-BI signal as binary data from the areageneration circuit, thereby generating a shadow.

Reference numeral 162 denotes a black character judgment circuit forjudging a feature of the image signal which matches with the originalimage before the color space compressing process at a high fidelity andgenerates thickness signals (degrees of bold characters) FTMJ of eightkinds of characters, an edge signal EDGE, and a color signal IRO to ablack character LUT 172.

By executing the black character judgment for the image signal beforethe image signal is converted by the color space compressing process,the black character judgment which matches with the original at a highfidelity can be performed and the image of a high picture quality can beobtained.

The invention is not limited to the apparatus for performing the blackcharacter judgment but can be also applied to an apparatus for judging afeature of an original image such as pattern recognition, black andwhite/color judgment of the original, or the like.

Reference numeral 108 denotes a color space compression circuit forperforming the following matrix arithmetic operation (1).$\begin{matrix}{\begin{pmatrix}R^{\prime} \\G^{\prime} \\B^{\prime}\end{pmatrix} = {\begin{pmatrix}R \\G \\B\end{pmatrix} + {\begin{pmatrix}{a11} & {a12} & {a13} & {a14} & {a15} & {a16} & {a17} & {a18} \\{a21} & {a22} & {a23} & {a24} & {a25} & {a26} & {a27} & {a28} \\{a31} & {a32} & {a33} & {a34} & {a35} & {a36} & {a37} & {a38}\end{pmatrix} \times \begin{pmatrix}{R - X} \\{G - X} \\{B - X} \\{\left( {R - X} \right) \times \left( {G - X} \right)} \\{\left( {G - X} \right) \times \left( {B - X} \right)} \\{\left( {B - X} \right) \times \left( {R - X} \right)} \\{R \times G \times B} \\{\left( {255 - R} \right) \times \left( {255 - G} \right) \times \left( {255 - B} \right)}\end{pmatrix}}}} & (1)\end{matrix}$

where, X denotes the minimum value of the input signals R, G, and B.

FIG. 3 shows a detailed diagram of a circuit for arithmeticallyoperating an R′ output in the color space compression circuit. Referencenumeral 301 denotes a minimum value extracting circuit for extractingthe minimum value X among the R, G, and B signals inputted to the colorspace compression circuit and for outputting the minimum value signal X.Reference numerals 302, 303, and 304 denote subtracting circuits eachfor obtaining a difference between the input signal and the minimumvalue signal. The subtracting circuit 302 outputs (R−X), the 25subtracting circuit 303 outputs (G−X), and the subtracting circuit 304outputs (B−X). Reference numerals 305 to 312 denote multiplyingcircuits. The multiplying circuit 305 executes a multiplication of [(amatrix coefficient all)×(R−X)]. In a manner similar to the above, themultiplying circuit 306 executes a multiplication of [a12×(G−X)]; 307 .. . [a13×(B−X)]; 308 . . . [a14×(R−X)×(G−X)]; 309 . . .[a15×(G−X)×(B−X)]; 310 . . . [a16×(B−X)×(R−X)]; and 311 . . .[a17×R×G×B], respectively. Since the signal inverted by an NOT gate 314is inputted, the multiplying circuit 312 executes a multiplication of[a18×(255−R)×(255−G)×(255−B)]. The signals multiplied as mentioned aboveare respectively added by an adding circuit 315 and is further addedwith an R signal by an adding circuit 316, thereby outputting as an R′signal. G′ and B′ signals are also generated in a manner similar to theforegoing R′ signal.

The term up to R−X to (B−X)×(R−X) executes the color space compression.The term of (R×G×B) executes a chromatic color substratum level control.The term of [(255−R)×(255−G)×(255−B)] executes a dark level correction.

The chromatic color substratum level control is executed inconsideration of a substratum color tone, namely, a substratum colorcomponent ratio.

Further, since the chromatic color substratum level control is performedby using the equation (1), the substratum level control can be executedon the basis of a function that is non-linear and continuous for theinput image data.

Therefore, by performing the chromatic color substratum level control,for example, when the user wants to erase yellow color as a substratumfrom an original having a yellowish color, only the substratum yellowishportion can be erased and other pale colors such as magenta differentfrom the yellowish color or the like.

Therefore, since an influence is hardly exerted on another pale color inwhich the user can erase only the unnecessary substratum, the user canexecute a desired substratum level control.

Moreover, since the sub stratum level control is executed on the basisof the non-linear and continuous function, a gradation can be preferablyreconstructed from the pale color in a color near the color tone of theoriginal from which the substratum is eliminated.

In the case where it is better not to perform the color spacecompression such as a case where the color space compressed color signalis inputted from the external apparatus, the CPU 130 switches the colorspace compression to an OFF state on the basis of the area signal AREA.

Namely, the color space compression is set to be through in an imagearea from the external apparatus shown by the IPU-BI signal.

When the color space compression is in the OFF state, the coefficientregarding the color space compression that is used in the matrixarithmetic operation (1) is set to 0.

Similarly, in the case where the chromatic color substratum levelcontrol is not performed, the coefficient regarding the chromatic colorsubstratum level is set to 0.

Therefore, in the case where the replacement synthesis of the image readby the CCD and the image from the external apparatus or the like wasexecuted, processes such that the color space compression is executed tothe image read by the CCD and the color space compression is notperformed to the image from the external apparatus can be executed. Asituation such that the color space compression is executed twice forthe image from the external apparatus can be avoided and an image whichmatches with the original at a high fidelity and hardly deteriorates canbe obtained.

Further, an editing process using a single image signal without mixingthe signal from the external apparatus to the read signal such as areplacement synthesis or the like can be executed to the same area bythe synthesizing (1) circuit provided before the color space compressioncircuit irrespective of whether the input signal is the signal from theexternal apparatus or the signal read from the CCD or whether the colorspace compression is necessary or not. The same editing circuit forperforming an edition such as synthesis or the like doesn't need to beprovided before and after the color space compression circuit. A circuitscale and the costs can be reduced.

In case of inputting the CMYK area-sequential image signals from theexternal apparatus, the CPU 130 is controlled so as to make the colorspace compression through for the image area from the external apparatusthat is designated on the basis of the IPU-BI signal.

By performing the substratum level control and dark level control of thechromatic color in addition to the color space compression by the matrixarithmetic operation (1) of the color space compression circuit, thecircuit scale and the costs can be reduced. A good image can be obtainedwithout exerting a fault to each correction by each correction.

Reference numeral 109 denotes a light amount-density conversion unit(LOG conversion unit) for converting the 8-bit light amount signals ofred, green, and blue to the 8-bit density signals of cyan (C), magenta(M), and yellow (Y) by the logarithm conversion, respectively.

On the basis of a LOGCD signal which is produced in an area LUT 173,which will be explained hereinlater, the LOG conversion unit 109executes the light amount-density conversion when the input signalformat is the RGB format and doesn't perform the light amount-densityconversion when the input signal format is the CMYK format.

Therefore, since the processes are changed on the basis of the inputsignal format, the optimum conversion can be performed for the inputsignal.

Further, since the processes can be made through in both of the colorspace compression circuit 108 and LOG conversion unit 109 as mentionedabove, there is no need to change a path of the signal in accordancewith the format of the input color signal and the circuit scale and thecosts can be reduced.

The LOG conversion unit 109 executes an achromatic color substratumlevel control for controlling a highlight portion by executing the samelight amount-density conversion in a lump for the RGB signals aftercompletion of the color space compression.

Different from the chromatic color substratum level control that isexecuted in the color space compression circuit 108 mentioned above,according to the achromatic color substratum level control, the samesubstratum level control is executed in a lump to each color componentof the input color signal irrespective of the chromatic color orachromatic color without considering the color tone of the substratum ofthe input color signal, namely, the color component ratio of thesubstratum.

Therefore, different from the foregoing chromatic substratum levelcontrol, since the control can be executed in a lump for the outputimage signal after completion of the color space compression, thesubstratum level control of the achromatic color can be executed. Ahighlight control in the achromatic color according to the output imagecan be performed and a good image according to the desire of the usercan be obtained.

Reference numeral 110 denotes an output masking processing unit toexecute well-known masking arithmetic operations for extracting thedensity signal of black from the density signals of three colors of C,M, and Y by a well-known UCR process (undercolor removing process) andfor eliminating a color turbidity of a developing agent corresponding toeach density signal. From the density signals of M′, C′, Y′, and K′formed as mentioned above, the signal of the color corresponding to thedeveloping agent that is used at present is selected by a selector 111.A ZO-TONER signal is a 2-bit signal which is generated from the CPU forcolor selection. When the ZO-TONER signal is equal to 0, the M′ signalis outputted as an READ-DT signal. Likewise, when the ZO-TONER signal isequal to 1, the C′ signal is outputted. When ZO-TONER is equal to 2, theY′ signal is outputted. When ZO-TONER is equal to 3, the K′ signal isoutputted.

Reference numeral 112 denotes a sampling circuit for sampling theinputted image signals R, G, and B and a density signal ND produced fromthe image signals R, G, and B every four pixels and serially outputtingas R, G, B, and ND signals. The density signal ND is expressed by, forexample, (R+G+B)/3. Reference numeral 113 denotes a selector forselecting the image signal READ-DT when an SMP-SL signal is set to the Llevel by the CPU and outputs. When the SMP-SL signal is set to the Hlevel, the selector 113 selects a sampling signal SMP-DT and outputs.

Reference numeral 164 denotes a synthesizing (2) circuit for openworksynthesizing the image signal read by the CCD and the image signal ofthe CMYK format that is inputted from the external apparatus 159. Whenthe CMYK synthesis is executed, the color signal corresponding to thedeveloping agent that is used at present is inputted one page by onefrom the external apparatus in accordance with the image signal from theCCD. The area to be synthesized is switched by the CPU 130 on the basisof the AREA signal, namely, IPU-BI signal in a manner similar to the RGBsynthesizing (1) circuit 157.

The processes for arithmetically operating a plurality of image signalsand producing an edition image signal for the same area like an openworksynthesis cannot be arithmetically operated unless a plurality of imagesignals have the same signal format. Therefore, with respect to the CMYKimage that is inputted from the external apparatus, the RGB signals readby the CCD are converted to the signals of the CMYK signal format by theLOG conversion or the like and, after that, they are processed by usingthe synthesizing (2) circuit.

Reference numeral 165 denotes a coloring circuit for executing aprocess, for example, for adding a preset color to a black and whiteimage. A color can be also added to a binary image signal IPU-BI fromthe external apparatus. Further, a gradation pattern such that thegradation gradually changes can be also formed. Reference numeral 166denotes an F value correction circuit for executing a gamma processaccording to the developing characteristics of the printer. A densitycan be also set every mode.

Reference numeral 114 denotes a zoom circuit, having a memory of oneline of the image signal, for executing an enlargement or reduction ofthe image signal in the main scan direction or an oblique copyingprocess for outputting the image in an oblique state. Upon sampling,sampling data is accumulated in the memory and is used to form ahistogram.

Reference numeral 168 denotes a texture circuit for synthesizing apattern obtained by binarizing the image signal which has previouslybeen read by the CCD or a binary pattern inputted from the externalapparatus to the color image signal read by the CCD and outputs asynthesized signal.

Reference numerals 169 and 170 denote a smoothing circuit and an edgeemphasis circuit each of which is constructed by a filter of (5×5).

Reference numeral 171 denotes an add-on circuit for multiplexing a codedpattern to specify the number which is peculiar to the apparatus to theimage signal and outputting the multiplexed signal.

Reference numeral 115 denotes a laser and laser controller forcontrolling a light emission amount of the laser in accordance with aVIDEO signal as a density signal of eight bits. The laser beam isscanned in the axial direction of the photosensitive drum 1 by thepolygon mirror 3 a and forms an electrostatic latent image of one lineonto the photosensitive drum. Reference numeral 116 denotes aphotodetector, provided near the photosensitive drum 1, for detecting apassage of the laser beam just before the photosensitive drum 1 isscanned and generating a sync signal BD of one line.

Reference numeral 173 denotes an area LUT (lookup table) circuit forsetting each mode in accordance with AREA signal from the areageneration circuit 160. The LOGCD signal as an output of the area LUTcircuit 173 is used for switching an LOG table of the LOG conversionunit 109 to a through setting or the like. A UCRCD signal is used forperforming a trimming or masking by the output masking processing unit110. An FCD signal is used to change a magnitude of an F value of theF-value correction circuit 166. An ACD6 signal is sent to the coloringcircuit 165. An NCD signal is sent to the synthesizing (2) circuit 164.The KCD signal is connected to a black character LUT circuit 172.Various modes are set, respectively.

Reference numeral 172 denotes the black character LUT circuit forexecuting various processes by an output of the black character judgmentcircuit 162. For example, a UCR-SL signal is used to execute processessuch that a UCR amount of the output masking circuit 110 is changed andan amount of black is further increased and amounts of C, M, and Y arefurther reduced for the area which is judged as a black character andthe development is performed and the like. An EDGE-SL signal is used toperform a setting to switch to a filter in a manner such as to emphasizean edge portion for an area of a black character in the smoothingcircuit 169 and the edge emphasis circuit 170. Further, an SNS-SL signalis used to switch the number of lines (400 lines/200 lines) of the PWMcontrol in the laser controller 115 for an output of the black characterLUT circuit 172. Namely, in the area judged as a black character, thedevelopment is performed by 400 lines in order to raise the resolution.In the other image areas, the development is executed by 200 lines inorder to raise the gradation.

As mentioned above, the black character judgment circuit 162 can judge afeature regarding a black character on the basis of the image signalwhich matches with the original image at a high fidelity before thecolor space compressing process is executed.

Therefore, the black character LUT circuit 172 can output a controlsignal to control each process for setting the black character in areproduction image to a high picture quality on the basis of the featureregarding the black character which was correctly judged.

Therefore, each process regarding the black character can be optimallycontrolled without being influenced by the color space compressingprocess.

Reference numeral 118 denotes a photosensor for detecting that thetransfer drum 5 a arrives at a predetermined position, generates a pagesync signal ITOP, initializes a sub scan address counter of the syncsignal generation circuit 104, and supplies the ITOP signal to the CPU.Reference numeral 130 denotes the CPU for controlling each block (notshown). That is, for example, the CPU 130 analyzes a protocol with theexternal apparatus and a status command and IPU-BI signal from theexternal apparatus and controls each block.

Reference numeral 131 denotes a controller for controllingforward/reverse rotation and a rotational speed of the read motor 35.Reference numeral 132 denotes an I/O port for controlling other sensorsand actuators which are necessary to control the copying operation. A PFsignal for feeding a paper from a paper cassette is also included in theI/O port 132. As another signal, a size of paper is detected by a papersize sensor (not shown) attached to the paper cassette and a sizedetection signal is inputted from the I/O port to the CPU. Referencenumeral 51 denotes the console unit for instructing the number of copiesand various kinds of operating modes such as color space compression,substratum control mode, and the like.

Reference numeral 133 denotes an ROM in which programs which are used inthe CPU and preset values have been stored. Reference numeral 134denotes an RAM to temporarily store data. Set values which are newly setand the like are also stored in the RAM.

In the above description, as a method of bypassing the processes of thecolor space compression circuit and LOG conversion unit, it is alsopossible to provide a selector circuit and to directly input to the nextprocessing circuit without passing through the processing circuit whenthe process is bypassed.

(Sequence)

A sequence for the color space compression will now be described withreference to a flowchart of FIG. 4. First in step 401, when the originalis placed on an original support plate glass and a copy start key isdepressed, an initialization is performed in step 402. In this instance,the selector 113 selects the output SMP-DT of the sampling circuit. Instep 403, a pre-scanning operation to read the image signal by theoptical system is executed. At this time, the image forming unit as aprinter doesn't operate. The image signals R, G, and B read in step 404are sequentially converted to the serial data by the sampling circuitunit in accordance with the order of R, G, and B (density signals) andare sequentially written into the memory of the conversion circuit. Inthis instance, a 3-dimensional histogram is formed on the basis of theinput image signals by the CPU. Portions of high frequencies ofhighlight portions are detected as substratum levels and are stored asRW, GW, and BW=(RGB)W. A color distribution is subsequently detected. Acolor distribution detection is performed for the color signal havingthe highest saturation among the color signals out of the colorreconstructing range of the color output unit with respect tofundamental primary colors (R, G, B, C, M, Y). For the respectivefundamental primary colors, the detected color distributions are storedin the following forms.

(RGB)R, (RGB)G, (RGB)B, (RGB)C, (RGB)M, (RGB)Y=(RGB)L

where,

L=1 to 6

Further, a dark level is detected. For example, among the signals inwhich all of the RGB signals are equal to or less than predeterminedvalues R_(PD), G_(PD), and B_(PD) such as

R<R_(PD) and G<G_(PD) and B<E_(PD)

the minimum signal is stored as a dark level (RGB)_(D). R_(PD), G_(PD),and B_(PD) show the R_(GB) signals of the darkest black color which iscolor reconstructed by the apparatus.

Matrix arithmetic operation coefficients are obtained in step 406.Namely, in the equation of the matrix arithmetic operation (1), 24values of the substratum level (RGB)_(W), color distribution (RGB)_(L),and dark level (RGB)_(D) detected in step 405 are set to the values R,G, and B before conversion. The maximum level which can be reconstructedby the apparatus for each of those values is previously stored as atarget and is set to the values R′, G′, and B′ after completion of theconversion of the matrix arithmetic operation (1). Thus, 24 simultaneouslinear equations are formed. By solving those equations, the matrixcoefficients can be calculated.

In step 407, the 24 calculated matrix coefficients all to a38 are setinto the color space compression circuit. The selector 113 selects theoutput READ-DT of the selector 111.

The paper according to the output image is fed in step 408. While theoptical system is moved, the original image is read and the image signalis matrix arithmetically operated by the color space compression circuitevery image synchronously with the reading operation in step 409. Instep 410, the magenta component signal M′ selected by the selector 111is developed as a VIDEO signal. In a manner similar to the above, thecyan component signal C′, yellow component signal Y′, and blackcomponent signal K′ are developed in accordance with this order, so thata full-color image is printed.

As mentioned above, by synchronously executing a series of operationssuch as image process and image formation as well as the reading of theoriginal image and the color space compression, the image can be formedin a real-time manner by the color space compression in consideration ofthe color reconstructing range of the device without needing the memoryof one picture plane.

In the above embodiment 1, it has been regarded that the image signalfrom the external apparatus was color space compressed, so that thecontrol has been made so as to set the color space compression to bethrough. The invention, however, is not limited to such a controlmethod.

Namely, as mentioned above, the image processing apparatus can receivesignals of various signal formats such as RGB image signals, CMYK imagesignals, and the like from the external apparatus.

Therefore, it is also possible to judge whether the color spacecompression is performed or not on the basis of the signal formatirrespective of the input destination of the image signal.

Specifically speaking, a control is performed so as to set the colorspace compression to be through for the RGB image signals and to executethe color space compression for the CMYK image signals. In thisinstance, the signal format is judged in a manner such that the imagesignals which are obtained from the CCD 34 are the RGB image signals. Onthe other hand, the signal format of the image signals which areinputted from the external apparatus is judged by the CPU on the basisof the status or IPU-BI signal.

The signal format of the input image signals can be also manuallydesignated by the console unit 51.

In the embodiment, although the color space compression circuit 108 andLOG conversion circuit 109 have been set to be through, it is alsopossible to construct so as to bypass those circuits.

<Embodiment 2>

The second embodiment of the invention will now be described in detailhereinbelow with reference to the drawings.

An image processing apparatus of the embodiment is constructed byfurther adding functions to the apparatus of the first embodimentmentioned above. The ON/OFF operations of the color space compression,substratum level correction, and dark level correction can beindependently manually set. FIGS. 5A to 5D show examples of a liquidcrystal display unit of the console unit 51 in the above firstembodiment. A key operation can be performed by a touch-key. In a window501, when a “substratum level control” key is touched, a display window502 is displayed. As shown in 502, in the substratum level control mode,there are an “A” key for performing a chromatic color substratum levelcontrol and a “B” key for performing an achromatic substratum levelcontrol. In the color space compression, there are an “ON” key and an“OFF” key.

Combinations as shown in FIG. 9 can be obtained by combinations of “A”and “B” of the substratum control mode and “ON” and “OFF” of the colorspace compression.

As shown in 502 in FIG. 5B, when a state (i) shown in FIG. 9 is set, thesubstratum control mode is set to “A” and the color space compression isset to “ON”. In this instance, by touching a “fine control” key, awindow 503 is displayed and a standard state when the chromatic colorsubstratum level control is performed can be independently set for eachof R, G, B, and Y. Further, by touching a “color space compression” keyor “OK” key in the window 503, the display is switched to a window of504 and a degree of the color space compression can be independently setfor each of R, G, and B. Further, by touching a “substratum level” keyin the window 504, the display is returned to the window 503. Bytouching the “OK” key, the display is returned to the window 502.

In the display screen of 502, a state (ii) shown in FIG. 9 is set, thesubstratum control mode is set to “A”, and the color space compressionis set to “OFF”. In this instance, by touching a “fine control” key, awindow of FIG. 6 is displayed. In a manner similar to the case of thestate (i), a standard state when the chromatic color substratum levelcontrol is executed can be set. In this instance, the color spacecompression circuit 108 is set to be through and the color spacecompression is not executed.

In the picture plane of the window 502, a state (iii) shown in FIG. 9 isset, the substratum control mode is set to “B”, and the color spacecompression is set to “ON”. In this instance, by touching the “finecontrol” key, a window 701 in FIG. 7A is displayed and a standard statewhen the achromatic color substratum level control is performed can beset. Further, by touching a “color space compression” key in the window701, the display is switched to a window 702.

In the picture plane of 502, a state (iv) shown in FIG. 9 is set, thesubstratum control mode is set to “B”, and the color space compressionis set to “OFF”. By touching the “fine control” key, a window as shownin FIG. 8 is displayed.

Namely, when the substratum control mode is set to “A”, as shown in thewindow 503 in FIG. 5C or FIG. 6, a density can be controlled in a rangefrom “dark” to “light” for each of the colors of R, G, B, and Y. Y isincluded as a parameter because substratums of many originals areyellowish.

Now, “dark” means that the substratum is densely displayed, while“light” denotes that the substratum is not so displayed. This means thatsubstratum levels Rw, Gw, and Bw are set for the controls of R, G, and Band on the basis of those values, the matrix coefficients of the matrixarithmetic operation (1) in the foregoing embodiment are calculated. Asthe “light” side is selected, the substratum levels Rw, Gw, and Bw areset to large values. Further, since yellow is a mixed color of red andgreen, when controlling yellow, the set values of the substratum levelsRw and Gw are interlockingly controlled. When the substratum controlmode is set to “B”, the density can be controlled in a range from “dark”to “light” as shown in 701. At this time, as shown in FIG. 10, thevalues of the lookup table (LUT) of the LOG conversion unit 109 arechanged or a plurality of preset LUTs are switched, thereby controllingthe substratums.

When the color space compression is set to “ON”, as shown in 504, themagnitude of the color space compression can be set with respect to eachcolor of red, green, and blue. As the magnitude of the color spacecompression approaches “large”, the color space compression effect islarge. In this instance, in accordance with each control of red, green,and blue, the values of the color distributions

(RGB)R, (RGB)G, (RGB)B, (RGB)C, (RGB)M, (RGB)Y=(RGB)L

where,

L=1 to 6

are set. On the basis of those values, the matrix coefficients of thematrix arithmetic operation (1) are calculated. As the magnitude of thecolor space compression approaches “large”, the value of the colordistribution (RGB)L can be largely set.

In step 503, an “A” key is used for auto density control (AE). Each timethe “A” is touched, the image display is black/white inverted and theON/OFF of theauto density control is set. When the AE mode is ON, thedensity control such as substratum control or the like is automaticallyperformed in accordance with “A” or “B” of the substratum control modeset in 502. In this instance, when the color space compression key is“ON”, the color space compression is also automatically performed. Whenthe auto density control key “A” is OFF, the substratum level control orcolor space compression is executed by using the value set in FIG. 8from the window 503.

Therefore, the user can select from the four kinds of combinations (i)to (iv) of the processes shown in FIG. 9 in accordance with the originalor a desired output image and can finely control in each mode. Theoutput image can be made closer to the original or a desired outputimage by the user.

For example, when the user wants to reconstruct a color tone in thecolor reconstructing range in accordance with the original at a highfidelity without being aware of the color tone of the portion out of thecolor reconstructing range, it is sufficient to set the color spacecompression mode to “OFF”.

In the substratum control mode “A”, namely, in the chromatic colorsubstratum level control mode, it is also possible to finely controlwith respect to a specific color such as Y or the like in addition tothe colors based on the signal format of R, G, and B or the like.Therefore, the user can easily perform the substratum level control ofyellow and chromatic color in the substratum or the like of, forexample, a yellowish original or the like without needing a specialknowledge about the specific color.

Further, since guidance messages indicative of input procedures aredisplayed as shown in FIGS. 5A to 8 with respect to the selection of thecombination of the processes and the fine control in each mode, the usercan easily set.

Further, after the copy was executed in the ON state of the auto densitycontrol, a value that is closest to each parameter of the automaticallycontrolled substratum control level and color space compression can bealso displayed from the console unit. In this instance, on the basis ofthe automatically set values, the user can further finely control thesubstratum level and color space compression. Moreover, by storing suchvalues of the substratum control level and color space compression intothe memory, they can be also called as necessary.

Those values can be also set by not only the console unit but also anexternal control apparatus or the like. Those values can be alsodirectly set by numerical values.

As mentioned above, the substratum level correction, color spacecompression, and the like can be also manually set.

<Embodiment 3>

The third embodiment of the invention will now be described in detailhereinbelow with reference to the drawings.

In the first embodiment, the foregoing color space compression circuit108 has executed the multiplication with the image signal for all of thematrix coefficients as shown in FIG. 3 when executing the matrixarithmetic operation (1) as shown in FIG. 3. One of the outputs of thesubtracting circuits 302, 303, and 304 in FIG. 3 is certainly set to 0.Therefore, one of the outputs of the multiplying circuits 305, 306, and307 is certainly set to 0. Two of the outputs of the multiplyingcircuits 308, 309, and 310 are certainly set to 0. Thus, the multiplyingcircuits can be simplified. FIG. 11 shows a detailed diagram of thecircuit for arithmetically operating the R′ output in the color spacecompression circuit 108 in the embodiment. Reference numeral 1001denotes a comparator for outputting a maximum value MAX, a medium valueMED, and a minimum value MIN for the three input signals R, G, and B.Reference numerals 1002 and 1003 denote subtracting circuits forexecuting arithmetic operations of (MAX−MIN) and (MED−MIN) and 1004 to1008 indicate multiplying circuits. The multiplying circuit 1004performs a multiplication of [a1a×(MAX−MIN)]. The multiplying circuit1005 executes a multiplication of [a1b×(MED−MIN)]. The multiplyingcircuit 1006 executes a multiplication of [a1c×(MAX−MIN)×(MED−MIN)].“a1a” and “a1b” denote coefficients corresponding to the terms of themaximum value MAX and medium value MED of the R, G, and B signals amongthe matrix coefficients “a11, a12, a13” of the matrix arithmeticoperation (1). “a1c” denotes a coefficient corresponding to themultiplication term of the maximum value MAX and medium value MED of theR, G, and B signals among matrix coefficients “a14, a15, a16”. Signal of[a17×R×G×B] are inputted to the multiplying circuit 1007. The signalsinverted by NOT gates 1009 are inputted to the multiplying circuit 1008and an arithmetic operation of [a18×(255−R)×(255−G)×(255−B)] isexecuted.

The signals multiplied as mentioned above are respectively added by anadding circuit 1010, respectively. The R signal is further added to anaddition signal of the adding circuit 1010 by an adding circuit 1011, sothat the resultant signal is outputted as an R′ signal. The other G′ andB′ signals are also produced in a manner similar to the foregoing R′signal.

As mentioned above, since the multiplying circuits are simplified in theembodiment, the costs of the hardware circuits can be further reduced.

The invention is not limited to the signal formats of RGB or CMY but canbe also applied to another format such as L*a*b*, YIQ, or the like.

The present invention can be also applied to a system constructed by aplurality of equipment or an apparatus comprising one equipment.

Although the invention has been embodied by the circuits as shown in theembodiments, it can be also embodied by a software.

It will be obviously understood that the invention can be also appliedto the case where it is accomplished by supplying a program to a systemor an apparatus.

The invention can be also applied to a head of the type for emitting anink jet by causing a film boiling by a heat energy and an imageprocessing apparatus to which a recording method using such a head isapplied.

Although the present invention has been described with respect to thepreferred embodiments, the invention is not limited to the foregoingembodiments but many modifications and variations are possible withinthe spirit and scope of the appended claims of the invention.

What is claimed is:
 1. An image processing apparatus comprising: inputmeans for inputting image data which indicates an input color by aplurality of different color components, image data of a plurality ofsignal formats being inputable by said input means and kind of theplurality of color components being different in each of the pluralityof signal formats; setting means for setting a color space compressionprocessing mode on a basis of a kind of signal format of the inputtedimage data; and color space compression processing means for performinga color space compressing process to the inputted image data on a basisof the set color space compression processing mode, wherein the colorspace compression processing mode includes a first mode in which thecolor space compression is performed and a second mode in which thecolor space compression is not performed.
 2. An apparatus according toclaim 1, wherein in a case where the signal format is a CMYK format, thesecond mode is set.
 3. An apparatus according to claim 1, wherein a casewhere the signal format is a RGB format, the first mode is set.
 4. Anapparatus according to claim 1, wherein said color space compressionprocessing means executes a matrix arithmetic operation.
 5. An apparatusaccording to claim 1, wherein in the second mode, said color spacecompression processing means is set to process the inputted image databy throughputting the image data without change.
 6. An apparatusaccording to claim 1, wherein said color space compression processingmeans is bypassed in the second mode.
 7. An apparatus according to claim1, further comprising judging means for judging the kind of signalformat of the inputted image data.
 8. An apparatus according to claim 1,further comprising: a scanner unit for scanning an original to producethe inputted image data; and an image forming unit for forming a colorimage on a recording medium, on the basis of color-gamut-mapped imagedata.
 9. An image processing apparatus comprising: first input means forscanning an original image and generating a first image signalrepresenting said original image; second input means for inputting asecond image signal representing an input image from an externalapparatus; and image forming means for forming an image on a recordingmedium in accordance with the image signal from said first or secondinput means, wherein said apparatus further includes color spacecompressing means for executing a color space compressing process on thefirst image signal inputted by said first input means and outputting theprocessed image signal and for outputting the second image signalinputted by said second input means without performing a color spacecompression on the second signal.
 10. An apparatus according to claim 9,wherein said external apparatus is an external memory apparatus.
 11. Anapparatus according to claim 9, wherein said external apparatus is afilm scanner.
 12. An image processing method comprising: an input stepof inputting image data which indicates an input color by a plurality ofdifferent color components, image data of a plurality of signal formatsbeing inputable by said input means and kind of the plurality of colorcomponents being different in each of the plurality of signal formats; asetting step of setting a color space compression processing mode on abasis of a kind of signal format of the inputted image data; and a colorspace compression processing step of executing a color space compressingprocess on the inputted image data on a basis of the set color spacecompression processing mode, wherein the color space compressionprocessing mode includes a first mode in which the color spacecompression is performed and a second mode in which the color spacecompression is not performed.
 13. An image processing method comprising:a first input step of scanning an original image and generating a firstimage signal representing said original image; a second input step ofinputting a second image signal representing an input image from anexternal apparatus; and an image forming step of forming an image on arecording medium in accordance with the image signal produced by saidfirst or second input step, wherein said method further includes a colorspace compressing step of performing a color space compressing processto the first image signal inputted in said first input step andoutputting the processes image signal and outputting the second imagesignal inputted in said second input step without performing the colorspace compression on the second image signal.